The radiation cross-linkable grades are already competing successfully with cross-linked conventional HDPE and polybutene-1 in hot water pipe applications in Japan. Processability reportedly approaches that of conventional Ziegler-Natta-catalyzed PE, thanks to a broad molecular weight distribution. Superior impact strength and ESCR, meanwhile, are derived from high comonomer content in high molecular weight chains. In Ziegler-Natta-catalyzed HPDE, the comonomer bonds primarily to shorter chains, while in conventional mPE they bond to both low and high molecular weight chains in roughly equal quantities.
Developmental injection molding grades combine high flow with impact strength or ESCR. Blowmolding grades featuring high stiffness, good impact strength, and high ESCR are also in the works. Finally, Asahi also aims to target the heat-resistant sealant film market with grades exhibiting high stiffness and transparency. Asahi Kasei Corp., Hibiya Mitsui Bldg., 1-1-2 Yuraku-cho, Chiyoda-ku, Tokyo 100-8440, Japan www.asahi-kasei.co.jp